1. Field of the Invention
The present invention relates to analog/digital converting apparatus that sequentially convert analog data input from external apparatus into digital form.
2. Description of the Related Art
There have been techniques for monitoring phenomena appearing as analog data (analog values)(for example, changes in temperature or in voltage), by use of an analog/digital converting apparatus (hereinafter will be called the “A/D converting apparatus”).
FIG. 4 shows a construction of a monitoring system which employs a previous A/D converting apparatus. As shown in FIG. 4, the previous monitoring system 100 includes an A/D converting apparatus 101 and an operation controller 110 having a CPU (Central Processing Unit).
The A/D converting apparatus 101 includes: a multiplexer (MPX) 102 which selects one of the channels CH1 through CHn; (here, n is an integer equal to or greater than 4 in this example) of analog data input from external apparatus; an analog/digital converter (hereinafter will be called the “A/D converter”; designated as “ADC” in the drawings) 103 which converts analog data of the channel selected by the MPX 102 into digital form; and a digital conversion value holding units 104 which temporarily holds the post-conversion digital data obtained by the A/C converter 103.
The operation controller 110 controls the MPX 102 to select analog data of channels CH1 through CHn in sequence in a periodic manner, and the operation controller 110 also reads out digital data which has been sequentially converted by the A/D converter 103 and then stored in the digital conversion value holding units 104.
Further, the operation controller 110 has a comparing units 111 which compares digital data obtained from the digital conversion value holding units 104 to thresholds that are associated with the channels of the obtained digital data. If the comparing units 111 detects that digital data of a certain channel exceeds its associated threshold, the operation controller 110 judges that the analog data of the channel is abnormal. The operation controller 110 then reads out digital data of all the remaining channels, and analyzes the cause of the occurrence of the abnormality.
That is, if the comparing units 111 detects any abnormal digital data, the operation controller 110 controls the MPX 102 to obtain digital data of all the remaining channels, and then analyzes the cause of the abnormality.
FIG. 5 shows an application of the monitoring system 100 that employs the previous A/D converting apparatus 101 of FIG. 4. As shown in FIG. 5, when the monitoring system 100 monitors voltage supply and temperature for individual elements [here, a CPU 121 and an I/O (Input/Output) device 122, and so on] making up the system board 120 of a UNIX™ sever, the MPX 102 of the A/D converting apparatus 101 receives voltage data from DDCc123 and DDCi124, which are power supplies (here, DC—DC converters) supplying the CPU 121 and the I/O device 122 with direct current, and temperature data from THc125 and THi126, which are thermistors measuring the temperatures of the CPU 121 and the I/O device 122.
As is already described with reference to FIG. 4, the monitoring system 100 monitors voltage supplies and temperatures for individual elements of the system board 120 of the UNIX™ server. If any abnormality occurs, its cause is analyzed.
In the monitoring system 100 of FIG. 4, every time the digital conversion value holding units 104 stores digital data therein, the operation controller 110 obtains the digital data so that the comparing units 111 compares the digital data to thresholds, which causes so large a load on the comparing units 111.
In order to reduce the load on the operation controller (CPU), techniques are proposed in which a comparing units is installed in the A/D converting apparatus, and in which an interrupt signal is output to the operation controller only when the comparing units detects any abnormality in digital data (for example, the following patent applications 1 and 2).
Further, another technique is also proposed in which a comparing units is prepared in the A/D converting apparatus. When the digital data is of a specific value, the processing on the A/D converting apparatus is switched into a processing mode corresponding to the specific value (for example, the following patent application 3).
[Patent application 1] Japanese Patent Publication No. 2002-261609
[Patent application 2] Japanese Patent Publication No. HEI 4-260915
[Patent application3] Japanese Patent Publication No. HEI 8-77133
In the monitoring system 100 employing above-described the previous A/D converting apparatus 101, if any abnormality is detected in digital data of one of the channels CH1 through CHn, the operation controller 110 uses digital data of the one channel and digital data of all the remaining channels, to analyze the cause of the occurrence of the abnormality. At that time, for attaining accurate analysis of the cause of the abnormality by units of the operation controller 110, it is preferred that not only the digital data of the one channel but also digital data of the remaining channels whose conversion is performed immediately after the conversion of the one channel is used in the analysis.
However, in the A/D converting apparatus 101 of FIG. 4, under a condition where the operation controller 110 performs other processing than the processing relating to the A/D converting apparatus 101, such other processing can make it impossible to read all the digital data necessary for the analysis from the A/D converting apparatus 101, even though the comparing units 111 detects any abnormality in digital data of one channel.
In addition, in the A/D converting apparatus 101, in order for the operation controller 110 to read all the other data necessary for the analysis, the operation controller 110 needs to control the MPX 102 to select the individual channels one by one to convert the data into digital form, and to read the digital data stored in the digital conversion value holding units 104 piece by piece. Because of this, it takes a long time to read all the other digital data even when the operation controller 110 can concentrate on the operation as the monitoring system 100 with no necessity for the operation controller 110 to perform any other processing.
In the techniques disclosed in the above patent applications 1 through 3, also, the operation controller halts the processing currently performed, upon receipt of an interrupt signal from the A/D converting apparatus, and obtains all the other digital data piece by piece, so that it takes a long time to complete the reading of the digital data. Further, in view of other processing to be performed, it can sometimes be impossible to read the required digital data without delay, thereby making it also impossible to read, with reliability, the digital data of all the other channels whose conversion is performed immediately after conversion of the one channel in which abnormality is detected.
In this manner, the aforementioned previous A/D converting apparatus has the following problem: even if any abnormality is detected in one channel of digital data, it is impossible to read out, with reliability, digital data of all the remaining channels whose conversion is performed after conversion of the one channel.